Heat exchangers for stirling cycle engines

ABSTRACT

A structural arrangement for a heat exchanger provides for movements without significant stresses of a heat exchanger in a Stirling Cycle Engine during changes of operating temperature. Two coaxial shell sections are arranged with a plurality of parallel heat exchange pipes axially mounted therebetween and affixed to the two sections. A flexible sealing element is sandwiched between the two shell sections to allow movement of the shell sections perpendicular to the axes of the heat exchange, pipes. A spacer separating the heat exchange pipes in the middle allow the pipes to bow as unit with evenly distributed deformation during temperature changes. Fluid conveyance pipes are connected to each shell section at the opposite ends of the heat exchange pipes.

United States Patent 1191] Hakansson 1451 Set. 10,1974

[ HEAT EXCHANGERS FOR STIRLING 2,963,871 12/1960 Meijer 165/81 x CYCLE ENGINES 3,121,559 2/1964 Tippman 165/83 [75] Inventor: g Angersdsamuel Hakansson Primary Examiner-Manuel A. Antonakas a we en Assistant ExaminerTheophil W. Streule, Jr. [73] Assignee: Kommanditbolaget United Stirling o y, g n FirmL8UfenC6 Brown (Sweden) AB & (10., Malmo, Sweden [57] v ABSTRACT [22] Filed: May 15, 1973 A structural arrangement for a heat exchanger provides for movements without significant stresses of a [21 1 App! 360578 heat exchanger in a Stirling Cycle Engine during changes of operating temperature. Two coaxial shell [30] Foreign Application Priority Data sections are arranged with a plurality of parallel heat May 19 1972 Sweden 23684/72 exchange Pipes axially mounted therebewee" and fixed to the two sections. A flexible sealing element is 52] us. c1. 165/81, 432/223 Sandwiched between the Shell Sections to allow 51 1m. (:1 F28f 7/00 movement of the Shell Sections Perpendicular to the [58] Field of Search l65/8l-83' axes of the heat exchange Pipes- A Spacer Separating 62/6 the heat exchange pipes in the middle allow the pipes to bow as unit with evenly distributed deformation [56] References Cited during temperature changes. Fluid conveyance pipes UNITED STATES PATENTS are connected to each shell section at the opposite ends of the heat exchange pipes. 1,439,283 12/1922 Astrom 165/81 2,229,344 1/1941 Schneider 165/81 x 3 Claims, 1 Drawlng Flgure I I Z t v 1 g 11 1A gf a 10 13 HEAT EXCHANGERS FOR STIRLING CYCLE ENGINES This invention relates to a tubular heat exchanger of the kind (herein called the kind defined) used as a cooler in a hot gas engine and comprising a generally cylindrical shell having end covers, a plurality of pipes through which working gas flows enclosed in the shell and extending in the axial direction of said shell and rigidly connected to said end covers, the said shell being provided with inlet and outlet openings for passing cooling fluid through the interior of said shell for contact with said pipes.

Known heat-exchangers of the kind defined are commonly arranged with one end cover adjacent to a cold gas connection duct leading to a compression space of the engine while the other end cover is arranged adjacent to a regenerator which in turn is connected to an expansion space of the engine through a heater head through which heat is supplied to the working gas.

With starting and stopping of the engine the heater head will be exposed to different temperatures, causing expansion and contraction of the heater head. In order to avoid excessive stresses in the heater head it has previously been proposed to allow for angular movements of a unit comprising regenerator and cooler by a suitable connection between the cooler and the cold gas connection duct. However, it has been difficult to solve the sealing problems which are serious because of the high pressure of the working gas.

The present invention is intended to provide an improved heat exchanger of the kind defined, capable of allowing movements of a hot gas engine heater head without the formation of substantial stresses.

According to the invention a heat exchanger of the kind defined is characterized in that said shell comprises two substantially co-axial shell sections having opposing end surfaces between which a sealing element is held so as to allow relative movements between said sections in directions substantially perpendicular to the axes of the shell sections.

The scope of the monopoly sought is defined in the claims hereinafter, and how the invention can be put into practice is explained in more detail with reference to the accompanying drawing, showing a vertical section through a heat-exchanger according to the invention by way of example.

The illustrated heat exchanger comprises an upper cylindrical shell section 1 integral with an upper end cover 2. An internally screw-threaded sleeve 3 is screwed on to said upper section 1, and a housing 4 containing a regenerator 5 is screwed into the sleeve 3. Pipes 6 adapted to be heated in a combustion chamber (not shown) are connected to the interior of the regenerator housing 4.

A lower cylindrical shell section 7 is mounted coaxially with the upper section 1 and is formed with a lower end cover 8. Numerous pipes 9 are arranged in parallel and secured to the end covers 2 and 8, thus preventing axial movements of the two shell sections 1 and 7 relative to each other except for relative movements due to thermal expansion and contraction. Leakage of cooling fluid is prevented by a sealing element 10 sandwiched or held between opposing end surfaces of the two shell sections 1 and 7. An external ring 14 serves to locate and protect the sealing element 10.

Inlet and outlet pipes 11 and 12 serve for circulating cooling water through the interior of the shell sections 1 and 7 in contact with the pipes 9.

A locating member 13 is mounted between the pipes 9 for locating the said pipes 9 relative to each other. The member 13, however, does not contact the inner surfaces of the shell sections 1 and 7.

A cold gas connection duct 15 connects the lower ends of the pipes 9 with a compression working space of a hot gas engine (not shown), and the pipes 6 at the top of the regenerator housing 4 lead to an expansion space of the same engine.

The heat exchanger as shown in the drawing will operate as follows:

Upon starting of the hot gas engine the pipes 6 will be exposed to rising temperatures, causing increases of dimensions. Such increases of dimensions would cause undesirable stresses in the pipes 6 if the pipe ends were prevented from movements.

In the connections of the pipes 6 to the expansion space (i.e. the cylinder of the engine) it is not practical to allow for expansion. Also the connection between the pipes 6 and the regenerator housing 4 must be made rigid. The heat exchanger as shown will, however, allow relative movements between the two shell sections 1 and 7, the pipes 9 being easily deformed to follow any relative movements of the shell sections in directions perpendicular to the axes of the said sections.

In other words, at a particular temperature the sections 1 and 7 are co-axial and the pipes 9 are straight, but at other temperatures the axes of the shell sections 1 and 7 are slightly offset in relation to each other and the pipes 9 are slightly bowed, but the sealing element 10, since it presses only against the end surfaces of the sections 1 and 7, allow the relative motions of the sections 1 and 7 in directions perpendicular to the axes thereof and prevents leakage of cooling water.

Thus following starting and stopping of the hot gas engine the stresses in the pipes 6 may be kept within acceptable limits.

The locating member 13 will ensure that the numerous pipes 9 will maintain their relative spacing in the transverse direction even when bowed or slightly deformed. As the member 13 does not contact the inner surfaces of the shell sections the deformations or bowing of the pipes 9 may be evenly distributed along their total lengths.

Althoughthe two sections 1 and 7 need not be of substantially equal axial length it is an advantage to arrange the member 13 in the vicinity of the sealing element 10 between the two sections, and the effect of the member 13 will be best if it engages midway between the ends of each pipe 9.

What is claimed is:

I. A tubular heat exchanger of the kind used as a cooler in a hot gas engine for conveying gases from a ments between said sections in directions substantially 3. A heat exchanger as defined in claim 1 wherein perpendicular to the axes of the shell sections. said inlet and outlet passages for conveying said cooling 2. A heat exchanger according to claim 1, characterfluid are respectively connected to different ones of ized in that said two shell sections are of substantially said two shell sections.

equal axial length. 5 

1. A tubular heat exchanger of the kind used as a cooler in a hot gas engine for conveying gases from a plurality of heated pipes to a gas duct connected with a compression working space of a hot gas engine, comprising in combination two generally cylindrical and co-axial shell sections each having end covers, a plurality of heat exchange pipes for carrying working gas extending axially within the shell sections and rigidly connected at opposite ends to said end covers, inlet and outlet passages for conveying cooling fluid into said cylindrical shell sections to contact said pipes, and a sealing element held between said sections allowing movements between said sections in directions substantIally perpendicular to the axes of the shell sections.
 2. A heat exchanger according to claim 1, characterized in that said two shell sections are of substantially equal axial length.
 3. A heat exchanger as defined in claim 1 wherein said inlet and outlet passages for conveying said cooling fluid are respectively connected to different ones of said two shell sections. 